Various types of torque wrenches have been employed when making up or breaking out drill pipe joints, drill collars, casing and the like in oilfield drilling and tubular running operations. Generally torque wrenches, which are sometimes also called power tongs or iron rough necks, include upper and lower tongs that sequentially grip and release upper and lower drill pipe joints with the upper and lower tongs being moved in a swiveling or scissoring manner to thread or unthread a threaded connection between the drill pipe joints. Power operated tongs have been provided for this purpose.
In some torque wrenches, an upper tong and a lower tong are swiveled with respect to each other by a torquing cylinder which can be extended or retracted to break out or make up the drill pipe as may be required. A pipe biting or gripping system on each tong utilizes moveable die heads that include pipe gripping dies. The die heads may be moveable by various means including, for example, hydraulic rams that extend to move the die heads into gripping or biting engagement with the pipe.